Owing to their harmful and polluting the environment, nitrogen oxides and sulfur dioxide are expected to monitor when they are used. However, the widespread use of gas sensing methods presents obstacles in terms of portability or stability. Hence, a better detect way needs to be found urgently. The success of graphene-based gas sensors has stimulated interest in two-dimensional (2D) materials in the gas sensing area. Transition metal dichalcogenides (TMDs), such as MoS2 or WS2, are considered to have the high-performance potential for gas sensors. Unfortunately, when used as a gas sensor, the sensing response of the pristine TMDs is greatly affected by a number of gas molecules that are too weak to be detected. Herein, to evaluate the sensing capability of Al, P, and Fe-doped WS2 to NO, NO2, and SO2, the molecular model of the adsorption systems was constructed, and density functional theory (DFT) was used to calculate the adsorption behavior of these gases. The binding force of all the doped-WS2 to the harmful gas molecules is much stronger than that of the pristine WS2. According to the results of adsorption energy, band structure, and state density, Aldoped WS2 has the potential to be used as NO and SO2 gas sensor, while P-doped WS2 is selective to NO. This work opens up a new reference for choosing appropriate doping types on 2D materials for noxious gas sensing.
The adsorption and reaction behaviors of a series of common gas molecules (CO, CO 2 , NH 3 , SO 2 , NO, NO 2 , and O 2 ) over defective and nonmetal (C, N, and O)doped MoS 2 monolayers in both the 2H and 1T′ phases have been systematically investigated using first-principles calculations. The most common defect (S vacancy) can significantly enhance the adsorption strength of all gas molecules. For defective 2H-MoS 2 monolayers, the S vacancies can be doped with C, N, and O atoms by passing the corresponding gases of CO, NO, and NO 2 /CO 2 at room temperature. However, this doping approach does not apply to defective 1T′-MoS 2 monolayers because of the high dissociation barrier of the adsorbed gases and other means such as electron beam irradiation has to be pursued. Moreover, O 2 and NO 2 catalytically dissociate over the defective and doped 2H and 1T′-MoS 2 monolayers. The O-doped sites in 1T′-MoS 2 monolayers can be reverted back to S vacancies by the CO adsorption. The N-doped 2H-MoS 2 monolayers are found to be a promising candidate for sensing CO and SO 2 .
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